Abstract

Accessory mitral valve tissue is a rare congenital cardiac
anomaly, and is usually incidentally detected in childhood. In
this case, we present a 65-year-old man with aortic stenosis
originating from an accessory mitral valve leaflet attached to
the anterior mitral leaflet. Interestingly enough, the patients
accessory mitral valve remained undetected for years until he
became symptomatic for degenerative aortic stenosis. Aortic
valve replacement and excision of the accessory mitral valve
attached to the anterior mitral leaflet was performed with a
transaortic approach instead of atriotomy. It was also unusual to
see accessory mitral valve tissue with aortic stenosis instead of
other frequently associated congenital anomalies.

Introduction

Accessory mitral valve (AMV) tissue is a rare congenital
cardiac anomaly and is usually diagnosed incidentally
for complaints such as shortness of breath, fainting,
chest pain, palpitation, and fatigue during childhood.
In some cases, it may lead to left ventricular outflow
tract (LVOT) obstruction. Accessory mitral valve
tissue is frequently associated with ventricular septal
defects, subaortic stenosis, large vessel anomalies and
atrial septal defects.[1] The incidence of AMV in adults
is estimated to be 1/26,000.[2] However, the prevalence
of AMV and the age in which it is most frequently
diagnosed are still debated.[3]

Although the exact embryological mechanism of
AMV formation is unclear, it may be caused by an
abnormal or incomplete separation of the endocardial
cushions.[4] Surgery is usually performed because of
severe LVOT obstruction or other cardiac reasons.[1]

Case Presentation

A 65-year-old male patient presented to our clinic
with complaints of exercise intolerance, palpitations,
and syncope. He had a history of stenting of the left
anterior descending coronary artery due to acute
coronary syndrome seven years previously. At that
time, no valvular pathology had been detected.
Physical examination revealed a 3/6 systolic murmur
over the aortic area. Other physical examination
findings and laboratory tests were normal. The patient
was on amlodipine and ramipril treatment for three
years. Transthoracic echocardiography revealed 60%
left ventricular ejection fraction. The ascending aorta
was 3.3 cm and the LVOT was 2.2 cm in diameter.
The aortic valve was tricuspid in nature, thick,
and calcified with maximum 65 mmHg and mean
36 mmHg transvalvular gradients. Planimetry showed that aortic valve area was 1.1 cm2. First degree aortic
regurgitation with minimal mitral regurgitation was
detected.

There was also a mobile thread-like structure
attached to the mitral anterior leaflet at the LVOT
and its echogenicity was similar to the mitral valve
(MV). The fixation area of this structure showed
coherence with the cord or papillary muscle. No other
congenital anomalies were detected. Preoperative
coronary angiography confirmed patent left anterior
descending stent. A surgery was planned for aortic
stenosis (AS) and aberrant tissue over the MV.
Perioperative transesophageal echocardiography
(TEE) was performed under general anesthesia and
showed a MV-like structure in the LVOT (Figure 1).
An echogenic parachute-like structure was present
over the anterior MV with dimensions of 35¥18¥8 mm
at the ventricular window. This structure was more
prominent at peak systole resulting in turbulence in the
LVOT. A transverse aortotomy was performed 2 cm
above the level of the aortic valve. Through the aortic
root, AMV was seen in the superior of the ventricular
aspect of the anterior MV, in the lower part of the left
leaflet of the aortic valve, and in the annulus with
two tendinous chord lesions (Figure 2). The AMV
leaflets were explored through the aortotomy in the
LVOT and excised without giving damage to other
MV structures. A number 19 mechanical valve was
replaced in the aortic position. Post-cardiopulmonary
bypass TEE showed that the AMV disappeared and the
mitral and prosthetic aortic valve functioned normally.
The postoperative period was uneventful. The patient
was discharged on fifth day with warfarin treatment.
Postoperative TTE was normal.

Discussion

Accessory mitral valve is often associated with
congenital cardiac anomalies in the pediatric patient
group. In adult patients, AMV may be a clinical
condition arising from the remote side, or it may be
diagnosed incidentally. The exact prevalence of this
anomaly is unknown because several cases of AMV
were incidentally diagnosed intraoperatively.[2]

As seen in this case, congenital AMV can remain
asymptomatic for many years. The literature reports
symptoms including dyspnea, syncope, chest pain,
palpitations and arrhythmias, cerebrovascular accidents,
low cardiac output due to subaortic obstruction, and
congestive heart failure.[1,2]

In symptomatic patients and patients who were
scheduled for cardiac surgery for different pathologies,
accessory valve resection is absolutely recommended.[3]
For isolated AMV, the current approach is intervention
in patients with significant LVOT gradient (mean
gradient of ≥25 mmHg). Patients with LVOT mean
gradient under 25 mmHg, are recommended to be
followed-up at regular intervals.[1,2]

Although TTE is sufficient for diagnosis,
perioperative TEE is helpful for both confirmation of
the diagnosis and evaluation of the MV functions after
excision.[5,6] Transesophageal echocardiography is also
important in the evaluation of possible complications
that may occur after excision and revision of
cardiopulmonary bypass for repair and completion of
the surgical procedure.

Despite limited experience in the fields of AMV,
and frequency of surgical treatment, and methodology in the literature, it is stated that AMV excision could
be performed via right or left atriotomy.[h aortotomy.
The AMV tissue was easily accessed through the
aortotomy side. We were able to perform excision of
the AMV without the need for atriotomy.
As a result, in patients with accessory mitral valve
tissue undergoing aortic surgery, the accessory valve
can be easily removed through aortotomy without
opening another heart chamber; therefore, potential
systemic side effects due to extension of extracorporeal
circulation can be avoided.

Declaration of conflicting interests
The authors declared no conflicts of interest with respect to
the authorship and/or publication of this article.

Funding
The authors received no financial support for the research
and/or authorship of this article.

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